| Abstract | As part of the research project conducted at IRC to evaluate the in-place emergency ventilation strategies of the L. H. - La Fontaine tunnel, this report investigates the fire dynamics in one section of the 1.8 km long tunnel. Computer simulations of fire scenarios were carried out, using a Computational Fluid Dynamics (CFD) model to gain insight into the effect of several parameters on the fire growth, thermal conditions and species concentrations in the tunnel. A section of the tunnel was simulated to optimize the cost of computations. In the first part of the study, a sensitivity analysis was performed to determine the effect of the computational grid size and length of the investigated section of the tunnel. The results of this analysis were used to determine the appropriate grid distribution and section length for the parametric study.Results from the sensitive study showed that the grid size influenced both the computation time and the prediction of the temperature and smoke. The numerical model predictions show that a 300 m long section of the tunnel was sufficient to investigate the ventilation configurations. A parametric study was conducted to investigate the effect of different ventilation configurations on fire-induced flows and conditions in the tunnel section. The parametric study indicated that when the side upper supply vents are open, higher temperatures and CO2 concentrations are observed in the evacuation path. In the roadway area, a smoke back-layering phenomenon was observed which may delay the removal of combustion gases and heat. In addition, a higher temperature was estimated at a height of 1.5 m compared to other supply side vent scenarios. It was concluded that the opening of the upper supply vents delayed smoke removal and, consequently, increased hazardous situations in both the traffic and escape paths. |
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